Replace the INTERPOLATED_PRESSURE and SENSOR_PRESSURE macros by
inline functions. Generate a common inline function that reads
a pressure value for a dynamic sensor.
Not all SENSOR_PRESSURE macros can be replaced, because the
macro is also used to set the value and C sadly doesn't know
the concept of "return reference from a function".
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>